(a) Field of the Invention
The present invention is related to a universal power adapter working with variable power socket specifications by nation, and more particularly, to a built-in adapter that allows only one pair of blades sticking out to insert into a socket for achieving electric conduction.
(b) Description of the Prior Art
More people travel around the world for pleasure or business thanks to the ever development of socio-economy, and they usually carry themselves some communication equipment or electric appliance on the road including notebook, handset, MP3, and other electronic products. Whereas all those electronic products relate to power consumption items, a matching adapter must be brought along for recharging purpose. However, different standards of communication interface are adopted in the world. For example, sockets in USA, UK, Europe, and Australia are not of same specifications. Therefore, the electronic product is usually not functioning when prevented form being recharged in a strange country. To solve this problem, one before the trip must find out the specification of the particular plug in the country of destination and purchase an adapter to match the plug. Preparation of the adapter becomes even more inconvenient when one's itinerary involves multiple stops in different countries and too many adapters must be brought before hitting the road.
To cope with the needs of people traveling around the world, a multi-purpose adapter is generally available in the market. The multi-purpose adapter is essentially related to a combination of adapters in specifications of multiple nations. However, when one particular set of plug is selected and inserted into a socket depending on the country the user stays, the user is exposed to risk of electric shock or shortage since the remaining sets of plug are also exposed and protruding from the adapter. Improvements are made to the multi-purpose adapter as taught in Taiwan Patent Publication No. TW541768 and China Patent Publication No. CN1539187A.
According to a multi-purpose adapter socket disclosed in the patent application of TW541768, a security device and a corresponding safety cover are disposed at where the operation takes place on the inner side of the socket in relation to the blades of the power; and a control rod and a locking block linked to a pushbutton indicates a status of lateral displacement to force each power blade locked in place while permitting only one set of power blade to be freed to extend for conduction. Accordingly, the adapter socket is provided with mandatory protection results to improve safe use. However, as the design of a product is smaller, thinner, and lighter oriented, the limited space available in the adapter socket is not in favor of accommodating those additional security device and safety cover. Furthermore, the operation of the adapter socket is compromised by its complicate structure since it is not uncommon when the pushbutton fails or gets stuck.
Another power plug disclosed in China Patent Application No. CN1539187A teaches a casing and multiple standardized plug contacts that movably supported in the casing. Each plug contact is disposed with two conduction blades and both blades are capable of moving out to get into a working location along a slide travel or into an idle location. The plug is characterized by that at least one braking member is mobile in relation to the casing and the terminal of the plug and the braking member is secured to a location externally to the idle location by means of a plug contact. When secured in place, the braking member is disposed at the slide travel designated for any of the remaining plug contacts to prevent another plug contact moving form the idled location into the working location. The option of the prior art as disclosed takes advantage of the braking member disposed in the slide travel to restrict the displacement by any other plug contact; however, the braking member as made in a mobile construction is vulnerable to get loosened up and/or shaking to result in either failure or getting stuck in operation. The prior art disclosed in China Patent Application No. CN1539187A further incorporates a security member in realizing the function of restricting the displacement by any other plug contact. Whereas the strict use of the security member to reach the purpose of restriction fails to bring smooth displacement of the plug, incorporation of a pushbutton is needed to facilitate displacement of the plug. Accordingly, the operation becomes awkward because that the user has to press the pushbutton with one hand and push out the plug with another hand to extend the plug. The operation tends to fail after frequent use of the plug.